Four diclofenac complexes with cobalt(II) and nickel(II) ions: synthesis, spectroscopic properties, thermal decompositions, crystal structures, and carbonic anhydrase activities

Cobalt(II) and nickel(II) complexes with diclofenac (dicl) in the presence of nitrogen-donor 3-picoline (3-pic) and 1-(2-aminoethyl)pyrrolidine (2-aepyr), [Co(dicl)(2)(3-pic)(2)] (1), [Ni(dicl)(2)(3-pic)(2)(H2O)(2)] (2), [Co(dicl)(2)(2-aepyr)(2)] (3), and [Ni(dicl)(2)(2-aepyr)(2)] (4), have been synthesized and characterized by FT-IR, UV-Vis, elemental and thermal analysis. The crystal structures of 1 and 3 have been determined by single-crystal X-ray diffraction; phase purity of complexes has been proved by powder X-ray diffraction analysis. Structural analyses have demonstrated that 1 and 3 are mononuclear and Co(II) ions have distorted octahedral environments. In 1, dicl is bidentate, whereas in 2, 3, and 4 dicl is monodentate. Dicl ligands are coordinated to metal(II) ions with O of carboxylate. Therefore, IR spectra of all complexes display {nu(OCO)(asym) and nu(OCO)(sym)} of dicl. The calculated Delta nu(OCO) values are consistent with the presence of monodentate (>200) and bidentate (<200) carboxylate. Compounds 2, 3, and 4 exhibit inhibition effects on human carbonic anhydrase-I. Compounds 3 and 4 show high thermal stability compared with 1 and 2.